AC performance, physical and mechanical properties of polypropylene/polyolefin elastomers blends

Polypropylene/elastomer blend materials with different content (20%., 25%, 30%) of elastomer are prepared by blending polypropylene and ethylene/octene copolymer elastomers(POE), polypropylene and styrene-ethylene / butylene-styrene triblock copolymer (SEBS). We test the properties of the blends by SEM, DSC, mechanical performance, DMA, breakdown performance etc., to investigate the micro morphology, crystallization properties, AC breakdown strength and mechanical properties of PP and blends. The results of SEM showed that the elastomer distributed evenly in PP, they formed “island structure”. With the content of elastomer increased, the concentration and size of island phase increased too. In the same composition, the island phase size of the SEBS/PP composite material is significantly smaller than that of the POE/PP composite material. The results of DSC showed that when the content of elastomer increased, the crystallinity of composite material decreased slightly, but the crystallization temperature (Tc) and crystalline melt temperature (T_m) did not change significantly. Tensile mechanical test results showed that the thermal extension deformation quantity of composite under 165 °C were greater than PP, with the content of elastomer increased, the result increased too. When the content of POE is 30wt%, the deformation quantity rose to 11%, the tensile yield stress of 30wt% SEBS composites decreased to 20.01 Mpa.DMA test results show that the elastic modulus decreased to about 750 Mpa with the component of 30wt% POE at 25 °C. Breakdown strength of the composites is generally lower than that of PP, but the composite with 25wt% SEBS almost keep the breakdown performance of pure PP. The “island structure” in PP/elastomer blends retains the mechanical strength of PP, reduces the hardness of material significantly and increases the toughness and flexibility of PP at the same time.